Any advise is appreciated!
Best answer by eztoril
FYI, I solved my problem with help from Google helpdesk.
We concluded together that every setting was indeed correctly setup, like the ‘Visitor announcement’ turned on, ‘Notification/Partner services’ turned on in the Assistant settings, in “Your data in the Assistant” - ‘Web & App Activity’ turned on incl. the check-boxes, etc.
These settings were all turned off and then on again in order to re-apply the settings, but no luck yet (even though it was perhaps good to re-apply it)
The thing that finally resolved my issue was to perform a factory reset of my Sonos One speaker (i.e. long-press ‘infinity’ button while re-inserting the power cable) and re-activate the Google Assistant link to Google Assistant. I double-checked the link to Google by asking “OK Google, what’s my name” and the reply was indeed my name, Martin.
After that check, I pressed the door bell button and the Sonos One said “It is someone on the front door”. :-)
Hope this helps others having similar problem.